Large and Uniform Single Crystals of MoS2Monolayers for ppb-Level NO2 Sensing

Recently, unprecedented interest has been immersed toward the synthesis of two-dimensional (2D) transition metal dichalcogenides via the chemical vapor deposition (CVD) system. Synthesis of a uniform and large-sized monolayer MoS2atomic thin film via CVD is still a major bottleneck owing to strong dependence on diverse associated growth parameters. In this work, we have proposed the most viable recipe which is suitable for controlling the nucleation density of Mo and producing a 90 μm-long MoS2monolayer crystal and (695 × 394.8) μm2large MoS2monolayered film on SiO2/Si and c-plane sapphire, respectively. Moreover, MoS2monolayer sensing performance has been thoroughly investigated for NO2exposure at room temperature with a varying response of 4-57.5 for the 100-100 ppm level. Furthermore, the MoS2monolayer sensor exhibits an ultrasensitive NO2detection with limit of detection and limit of qualification values of 1.4 and 4.6 ppb, respectively. In addition, the first-principles-based density functional theory has been employed to analyze the adsorption of NO2on the surfaces of the 2D MoS2monolayer. It is observed that the electronic band gap of the MoS2monolayer after NO2adsorption is reduced by 0.7 eV due to molecular orbital hybridization.